Cottoniella fusiformis Børgesen

Scientific Description

Habit and structure. Thallus light pink to red, with prostrate axes to 20 mm long and erect axes to 12 mm tall. Prostrate axes 250–350 µm wide, attached by multicellular branched rhizoids arising singly from the distal cell of each pair of flanking cells, the flanking cell protruding laterally before cutting off the rhizoid. Rhizoids to 1.5 mm long, the cells 12–15 µm diam. [L:B 4–6], tapering to cells 7–8 µm diam. Erect axes 200–250 µm wide, slightly narrowed at the base and tapering evenly to the apices. Unbranched monosiphonous filaments arising singly or in pairs unilaterally from concave surface of branch apices, to 1.2 mm long, with cells 12–17 µm diam. [L:B 3.5–6]. Basal and suprabasal cells of monosiphonous filaments c. half as long as distal cells, the basal cell forming secondary pit connections with the proximal pericentral cell; most cells of similar width and tapering only slightly to rounded apices. All axes with 4 pericentral cells; each lateral cell cutting off a pair of flanking cells. Polysiphonous lateral branches arising from concave surface every 5–10 segments. Lower axes lightly corticated by adventitious filaments arising from pericentral cells.

Reproduction. Not seen in Australian specimens.

Distribution. Known from the Canary Islands, Madeira, Libya, Pakistan and Australia.

Habitat. epiphytic in the subtidal.

[After J.M. Huisman in Algae of Australia: Marine Benthic Algae of North-western Australia, 2. Red Algae: 585 (2018)]